1. Field of the Invention
The present invention relates in general to the field of energy management systems, and in particular, to systems, computer program code, and methods related to simultaneously synthesizing cost-effective combined heat and power utility systems and the process plant's heat exchangers network and distillation network sequence.
2. Description of the Related Art
Many different types of processes consume multiple steam levels and electricity to obtain an output result, or to produce a required product or compound. For large-scale processes that consume significant amounts of steam, it is preferable to optimize the consumption of energy through careful operation, design or reconfiguration of the plant and the equipment used. Further, in some industrial manufacturing processes, specific streams of material flows need to be supplied to different types of equipment and machinery at specific temperatures. These material flows may need to be heated or cooled from an original starting or supply temperature to a target temperature. This, in turn, will require the consumption of steam to heat specific streams and consumption of water, for example, to cool down specific streams. Energy to heat or cool down the specific streams can come from utility plant systems and/or through a network of heat exchange units which can recover potentially lost energy, reducing the amount of energy needed from the utility plant systems.
In nowadays mega complexes, the cost of fuel, power and its infrastructure as well as the site process heat exchangers network (HEN) and distillation network can be huge. A total site utility system in a chemical processing site, interlinked to the chemical plants production processes, for example, provides heat and power to chemical production processes. The economic performance of the total site utility systems directly influences the operating cost of the chemical processing site, hence it is recognized by the inventors that improvements in the synthesis of process subsystems and the total site utility systems can lead to significant savings.
Two basic approaches have been developed for the synthesis of utility systems (CHP). The first one is based on thermodynamic performance of the plant and aims in maximizing the plant's overall energy efficiency. Some optimization techniques may be included as part of the solution procedures. The second approach only uses optimization methods such as, for example, MILP and MINLP to satisfy the predefined targets/demands. In the methods that have been employed in both commercial software (e.g. Aspen Utilities Planner of Aspentech, Star software of university of Manchester/PI department, and ProSteam of KBC) and academic literatures, the task has been to design a utility plant that satisfies given/specific steam and power demands. This approach was later extended to account for uncertainty and disturbance in such one-time given/specific power and steam demand to multi-periods of again specific/given power and steam demand.
The state-of-the-art methodology presently adopted by the industrial community (e.g., process engineering departments) and academia, is also employed without systematic consideration of both distillation columns subsystem best sequence, design and operating conditions, and HEN synthesis, as well as best design conditions using high fidelity utility CHP details. The inventors have recognized that such approach is performed without considering the process degrees of freedom in the design of HEN, large distillation network sequence, or small but important groups of distillation network sequence or using the best process conditions to enable the best synthesis of the utility system. That is, recognized by the inventors is that the state-of-the-art fails to recognize or employ simultaneous syntheses of such subsystems, CHP, distillation columns, HEN, and/or the rest of process conditions. The numerous potential combinations of the degrees of freedom in both utility system and the key process systems such as, for example, HEN and process distillation network sequence and process design and operating conditions, however, can allow significant opportunity for both systems' syntheses optimization.
The combination of the two approaches as been demonstrated. Neither one of the combined approaches addressed the simultaneous synthesis of key process systems, such as, for example, the distillation sequence system, the HEN system, much less taking into consideration all possible combinations of process changes in the rest of the process such as temperature, pressure, reflux ratio, inter-coolers, and inter-heaters, in distillation columns, and so on, with the utility system synthesis.
In order to try to “optimize” energy recovery in both the process and the utility plants, the state-of-the-art has generally attempted to solve the synthesis problem by utilizing two entirely decomposed optimization problems: one for the chemical/process plant and one for the utility plant. Those two problems are currently solved in most of the companies by two different teams, either located in two separately decentralized departments within the same company, or in two different companies with the first being in the process plant and the second being in the utility plant. According to such conventional methodology, the process synthesis team/group dictates the process steam demand and process steam generation as well as equipment driver's type (motor or steam) to the utility subsystem (CHP) synthesis team/group, ahead of the CHP synthesis.
As such, the utility system synthesis problem is always addressed in both industry and academia as a “follower” objective problem. The process is always synthesized first and its process conditions are set. Thereafter the desired steam quantity and quality are defined to the utility system. The decision for process liquid and gas driving using motors driven or steam turbine driven pumps and compressors are decided ahead of the utility system synthesis. Such arguably archaic approach applied by managers in the decentralized company office emanates from an adherence to decisions made in the past, where the utility system was merely a bunch of boilers and the major capital in the facility was the process systems (e.g., distillation and HEN subsystems).
Recognized by the inventors, however, is that as a result of the new era of cogeneration, tri-generation and even quadra-generation where power and water emerged as new products, it may be more economically prudent to “change the chairs” such that the process systems, such as the HEN and distillation network, become the “follower” and the “utility system” becomes the “leader”. The inventors further recognize that the “utility system synthesis guy” can provide better results where his counterpart “process synthesis guy” cooperates, especially if the capital cost of the utility system is much higher than that of HEN and/or distillation network. Naturally, effective management of such utility systems syntheses can render big impact on projects' profitability and life cycle success.
Nevertheless, also recognized is that even in case of the closeness in capital cost between the utility system and the process system, the problem may become one of conflicting design objectives types. The problem can also become a little more complicated when the designer and/or the owner of the central utility system providing utilities to the chemical complex is a “third party” (other than the chemical company owner) who may have an investment plan of his own and limited project budget, and/or may represent the country national power grid. In such case, conflicting objectives may arise that may need to be addressed and solved between the chemical complex owner and the utility system owner in order to produce a result which satisfies both parties. Hence, it is recognized that there is a need for a different solution approach than the currently available in both industry and academia.
Correspondingly, recognized is the need for systems, computer program, and methods synthesizing cost-effective combined heat and power (CHP) utility systems and the process plant's heat exchangers network and distillation network sequence, which can identify its/the best key design and operating conditions in both partially and totally decentralized environments in order to address the problem of obtaining an optimal tradeoff among the CHP utility system synthesis and the key process units (HEN and distillation sequences) syntheses in mega facilities, which require many complex and huge interactions to be explored for best economic decisions.